Since conventional wood bits are so expensive to manufacture and so difficult to maintain and keep sharp, it has become customary in many cases to use a spade-type bit for drilling holes in wood or the like. Generally speaking, the spade-type bit has the advantage that it is simple and inexpensive, as well as easy to sharpen. In the simplest type the leading edge of the spade and the edges of the central point that extends from it are ground with a relief to give a cutting edge. In order to improve the speed of cutting, it has been suggested that the point be provided with grooves. For instance, in the patent of Robinson U.S. Pat. No. 2,782,824, grooves were formed along the cutting edges of the point. In the patent of Porter U.S. Pat. No. 3,997,279, grooves are formed as concave cylindrical surfaces which were symmetrical of the center line of the point. While these designs give excellent cutting, they are also considerably more expensive than the ungrooved spade-type bit. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a wood bit which, while relatively inexpensive, is capable of efficient cutting operation.
Another object of this invention is the provision of a wood bit which can be readily sharpened by an inexperienced person and without the use of extraordinary tools.
A further object of the present invention is the method of inexpensively making a spade-type wood bit.
It is another object of the instant invention to provide a wood bit which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service with a minimum of maintenance.